Memory T cells contain large amounts of mRNA for certain chemokines, including RANTES, MIP-1alpha and MIP-1beta. This mRNA is not translated, however, unless the cells are stimulated via their T cell receptors. Experiments will be performed to find out what portion of the chemokine mRNAs is involved in the silencing and which signaling pathways induced by T cell receptor engagement release the mRNAs from translational inhibition. Memory T cells may use these stores of preformed chemokine mRNA for very rapid responses to antigen. A protocol will be established to find out whether this is so, in animals.